Feeding mechanism for automatic guns



March. 25, 1952 R. s. SANFORD FEEDING MECHANISM FOR AUTOMATIC GUNS Filed April 12, 1946 l5 Sheets-Sheet l IN VEN TOR.

March 25, 1952 R. s. SANFORD 2,590,214

FEEDING MECHANISM FOR AUTOMATIC GUNS Filed Apr-i1 12, 1946 15 Sheets-Sheet 2 March 25, 1952 R. s. SANFORD FEEDING MECHANISM FOR AUTOMATIC GUNS 15 Sheets-Sheet 5 Filed April 12, 1946 WNN Lib-5 INVENTOR.

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FEEDING MECHANISM FOR AUTOMATIC GUNS Filed April 12, 1946 15 Sheets-Sheet 6 IN V EN TOR.

March 25, 1952 R. s. SANFORD 2,590,214

FEEDING MECHANISM FOR AUTOMATIC GUNS Filed April 12, 1946 15 Sheets-Sheet 7 INVHVTOR.

March 25, 1952 R. s. SANFORD 2,590,214

FEEDING MECHANISM FOR AUTOMATIC GUNS Filed April 12, 1946 15 Sheets-Sheet 8 ZZ/E/a mpzwzz a @2 March 1952 R. s. SANFORD v FEEDING MECHANISM FOR AUTOMATIC GUNS l5 Sheets-Sheet 9 Filed April 12, 1946 March 25, 1952 R. s. SANFORD 2,590,214

FEEDING MECHANISM FOR AUTOMATIC GUNS Filed April 12, 1946 15 Sheets-Sheet l0 I N VEN TOR.

March 25, 1952 R. s. SANFORD FEEDING MECHANISM FOR AUTOMATIC GUNS 15 Sheets-Sheet 11 Filed April 12, 1946 INVHVTOR.

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FEEDING MECHANISM FOR AUTOMATIC GUNS Filed April 12, 1946 15 Sheets-Sheet 15 Jim W mam- TRAVEL TO MOVE ROUND FROM TOP OF ,IOVERTRAVEL ouro ear-ram OF MOUTH 7.5 2.

BELT PITCH DISTRNCE- BOL 4| CLOSED AND FEEDER SPRING 516 T0 CHARGE GUN AIR PRESSURE l5 APPLIED .HT

UNCHARGED- 525, Sol-T 4-1 6055 BACK AND PAwLs 70l-7a2 To START BELT 0F AMMUNITION, BELT ARE MOUED To DOTTED LINE Posmou, SPRING l5 \NSERTED m FEEDER UNTIL ROUND 1 5w BEING CHARGED. AIR PRESSURE \5 RELEASED AND s ams 5|o MOVES PAWLS- 701402 To FULL LINE pvslncm. son MOVES FORWARD R ND 1 (5 NO RESTING 0N PewLS 755-756 l5 CAUGHT BY PHWL 724.

AS BOL 605 FORWARD IT DRIVES ROUNDJ OUT OF MOUTH AND CHAMBERS THAT ROUND. ROUND2 N W N -5 7 5-756 GUN CHARGED AGAIN BY REsToRme AIR PRE55URE sour 4| GOES BACK. PAWLS 701- GO'TO DOTTED LINE POSITION AIR PRESSURE RELEASED AND SPRING slo MOVES PAUJL-S v 701 ?z To FULL mus ?osno ammo 2 INVENTOR. FORCES RouNDl TO Berra/ 1 OF MOUTH 752 f AND IN PATH 0F Barr. ROUNOS 1AND2 HELD mTeRMemm-E Moum 752 mm FINGERS 566 y AND 568 RN BELT RESTRRINED AGRIN T MOVEMEN LONGITUDlNALl-Y- March 25, 1952 s, RD 2,590,214

FEEDING MECHANISM FOR AUTOMATIC GUNS Filed April 12, 1946 15 Sheets-Sheet 14 6A5 PRESSURE UNLOCKS BOLT AND BOLT ROUND 1 BEING EXTEAC'I'ED, PROJECTILE STARTS BACK. 6A5 PRESSURE ALSO CHARGES HA5 LEFI MUZZLE AND GAS P2655028 SPRING 0- TH FEED PawLs 701-702 MOVE mom is BEING DISSIPATED. SPRING 6w DOTTED TO Fun-L LINE Poslrlou- EXTEACIOR lol MOVE-5 PAWl-S 70l-702 TO Paslnolv l5 WITHORAWING EMPTY CASING .1 FROM SPEECH SHOWN THUS PLACING ROUND 2 ON TOP OF BOLT. ROUND 3 IS BEING 5T?|PP5D FROM n's LINK 564-- BOLT BOES FORWARD- EACH SUCCEEDING O ND REFER 5 '65: 35,36 378ND sour IS BACK AND READY 170 e0 3 u T F 36 FORWARD. spams Slo HAS MOVED PAWl-S 701-702 AND ROUNDS TO POS IONS SHOWN- ROUNDZ IS NOW IN PATH OF son, ROUNDS 2mm: HELD INVENTOR- IN EQMEOIATE MDUTH 752 AND FINGE S F66 AND 568. AND BELT eesnmmsn ABR BY LONslTUDINfll- MOVEM ENT March 25, 1952 R. S. SANFORD FEEDING MECHANISM FOR AUTOMATIC GUNS Filed April 12, 1946 SHORT LOOP ON NEXT TO LFIST ROUND IS FASTENED TO BRIDGE OF LAST ROUND 5O Lone LOOP 0F LAST ROUND (L. R.) CAN NOT ROTATE sun STOPS WITH LAST ROUND (L.R.) IN

POSITION SHOII I BEING RE5TRHINED FROM ENTERING MOU'IrI BY LAST ROUND HOLDIN6 PHWLS 755- 756. THUS LAST 15 Sheets$heet l5 NEW BELT (A) 1.5 INSERTED IN FEEDER. GUN IS CHARGED AND PAM/LS 7o1-7o2 ARE MOVED TO DOTTED LINE POSITION BOLT STARTS BAC K.

ROUND CANNOT BE FIRED AND GUN $TOP5 FIRING.

BOLT IS BACK. FEEDING 0F BELT HA5 MOVED LAST ROUND" TO BOTTOM OF MOUTH IN I POSITION TO BE PICKED UP BY BOLT 95 IT MOVES FORWARD. LAST ROUND HELD BY' FINGERS 566-568, ROUN 1A AND MOUTH 752,

IN VEN TOR.

SPRING 51o HAS BEEN ca-meeeo AND RELEASED, THUs MOVING BELT "A" FORWARD AND PLACING "LAST ammo ON TOP OF BOLT 4-I AS IT MOVES BACK Patented Mar. 25, 1952 FEEDING MECHANISM FOR AUTOMATIC GUNS Roy S. Sanford, Woodbury, Conn., assignor to The Autoyre Company, Incorporated, Oakville, Conn., a corporation of Connecticut Application April 12,1946, Serial No. 661,545

14 Claims. 1

This invention relates to automatic guns, commonly known as machine guns, for firing projectiles, and more particularly to guns of that class adapted, after once being set into operation, to continue to fire automatically as long as the trigger is held in released position.

One of the basic difficulties with many of the heretofore known guns of the aforesaid type has been their-unreliability in so far as feeding of the cartridges is concerned. When it is considered that the rate of firing of guns of this type is intended to be 600 to 700 rounds per minute, it will be apparent that the feeding mechanism must, to the greatest practicable extent, be free from jamming and misfiring, and that difiiculties are encountered at these high firing speeds. Prior types of feeding mechanism have suffered from these defects, and accordingly one of the principal objects of the instant invention is to provide feeding means which is reliable to a greater degree than prior feeders for automatic guns wherein the ammunition is preliminarily loaded into a belt including a plurality of links, each link serving to carry a round to the gun. The belt is ordinarily carried in an appropriate magazine adjacent the gun,

and during the feeding operation the links, each holding its individual cartridge, are successively fed to the mouth in the receiver.

The principal object of my invention is to provide in an automatic gun, feeding means utilizing the individual links of a flexible cartridge belt as part of the operative mechanism for transferring the cartridges from the belt to the receiver of the gun.

An additional object is to provide, in connection with the feeding means as aforesaid, means whereby surges in the belt are obviated, and together therewith the errors of loading and firing incident on such surges are eliminated.

A further object is to provide, in connection with the feeding mechanism as described, cam means whereby a round is rapidly and accurately dislodged or stripped from its link for delivery to the mouth in the receiver.

Another object is to provide, in connection with cartridge-holding links as aforesaid, means whereby a cartridge, after having been stripped, is securely held in the mouth by the succeeding cartridge.

Still another object is to provide, in connection with the feeding mechanism as aforesaid, means for securely positioning the last round of a particular belt in the absence of a following round, and to prevent said last round from being delivered to the receiver until a following round is positioned thereagainst for properly feeding the last round to the receiver in a predetermined position.

Still a further object is to provide a feeding mechanism which is capable of proper performance regardless of the position of the gun, for example, when installed on aircraft wherein the principal axis of the gun may be in any direction.

Another object is to provide a releasing mechanism for the feed pawls aforesaid which is capable of actuating the pawls irrespective of the position of the slide in its stroke.

In carrying out my invention in one form, I provide means co-operating with the feeder mechanism for bringing the cartridges from a suitable magazine adjacent the gun to the receiver of the gun, which means includes a plurality of link members interconnected to form a flexible belt, each cartridge being held in an individual link by means of resilient fingers. The feeder mechanism includes a stripping cam adapted to engage a portion of each link and the cartridge gripped thereby to displace the cartridge from its engagement with-the link and into a position from which it passes to the mouth of the receiver. The pioportioning and spacing of the fingers, cartridges, and receiver mouth are such as to insure that a cartridge after being stripped is resiliently maintained in a predetermined position in relation to the receiver, this being accomplished by providing the mouth with portions for retaining a cartridge prior to its engagement by the bolt for chambering, and delivering the succeeding cartridge in abutting relation to the retained cartridge, the fingers from which the later cartridge has been stripped exerting resilient force against said later cartridge. By maintaining engagement of the resilient fingers with the cartridge just stripped, backlash of the belt is effectively prevented, the cartridge and belt thereby co-operating each to maintain the other in a predetermined relation.

The feeder assembly is arranged to be quickly disengaged from the gun proper for ease in overhauling and maintenance and to permit the invention to be readily adapted to various types of guns, and comprises a base, a housing carried on the base, and a reciprocable member adapted to slide in suitable guides in the housing. A bell-crank lever is pivoted on the housing, one end of the lever being adapted to reciprocate the slide, the other end being given the necessary feeding motion by expansion of a spring, and being returned to normal by gas pressure derived from the explosive charge. The spring is adapted to be loaded by gas pressure operated devices to be hereinafter detailed and, although forming part of the structure in which the instant invention is embodied, are not claimed herein. Such gas pressure devices, as well as other details of the gun, are also described and broadly claimed in a co-pending application of Earle C. Bunnell, Serial No. 756,743, filed June 24, 1947, and entitled Automatic Gun, which application is assigned to the same assignee as the present invention.

In the drawings:

Figure 1 is a perspective view showing the left-hand side of the gun;

Fig. 2 is a perspective view showing the righthand side of the gun;

Figs. 3a and 3b constitute one view, being a left-hand side elevation of the gun, the view being broken into two parts as indicated by the dot and dash line in order to fit the limitations of the sheet;

Fig. 4 is a longitudinal cross-sectional view of a portion of Fig. 3a, and somewhat enlarged to show the bolt unlocking piston and vent plug;

Figs. 5a and 52) comprise one view, showing a plan of the gun with certain parts cross-sectioned, the view being broken as indicated by the dot and dash line in accordance with limitations of sheet size;

Figs. 6a and 6b constitute a single view, showing a left-hand side elevation with certain parts of the gun indicated in longitudinal cross section;

Fig. 7 is a cross-sectional view taken on a horizontal plane passing substantially through the axis of the gun;

Fig. 8 is a combined cross-sectional and lefthand elevational view of the gun taken substantially in a vertical plane through the axis of the gun;

Fig. 9 is an exploded perspective view showing the bolt, the breechblock slides, the breechblock lock, the extractor and minor parts appurtenant thereto; 4

Fig. 10 is a cross-sectional view taken substantially on the line Ill-l of Fig. 8;

Fig. 11 is a cross-sectional view taken substantially on the line I ll l of Fig. 6b;

Fig. 12 is a cross-sectional view taken substantially on the line I2I 2 of Fig. b;

Fig. 13 is a cross-sectional view taken on the line |3-|3 of Fig. 11;

Fig. 1 is a cross-sectional view taken on the line l4--I4 of Fig. 11;

Fig. 15 is a cross-sectional view taken substantially on the line I5--l5 of Fig. 6a;

Fig. 16 is a cross-sectional view taken substantially on the line [6-16 of Fig. 6a;

Fig. 1'7 is a cross-sectional view taken on the line l|-ll of Fig. 6a;

Fig. 18 is a view in elevation and cross section showing the bolt unlocking yoke and guide;

Fig. 19 is a detail, viewed from the front of the gun, of the bolt charging cylinder;

Fig. 20 is a cross-sectional view taken substantially on the line 20-20 of Figs. 6a and 6b;

Fig. 21 is a cross-sectional view taken substantially on the line 2 l2l of Fig. 7;

Fig. 22 is a partial view, somewhat enlarged, of a portion of Fig. 5a to show details of the pneumatic system;

Fig. 23 is a cross-sectional view taken axially of the bolt charging cylinder and certain parts appurtenant thereto;

Fig. 24 is a view looking toward the rear of the gun and showing the bolt charging cylinder, feeder operating cylinder, and certain connections therebetween;

Fig. 25 is a cross-sectional view of a portion of one of the recoil cylinders;

Fig. 26 is a detail showing a round assembled with its link and in relation to the stripping cam;

Fig. 27 is a cross-sectional view on the line 2121 of Fig. 26;

Fig. 28 is a cross-sectional view on the line 28-28 of Fig. 26;

Fig. 29 is a cross-sectional view taken on the line 2929 of Fig. 3b;

Fig. 30 is a cross-sectional view taken on the line 30-30 of Fig. 29; and

Figs. 31 to 42, inclusive, represent in diagrammatic form various steps in the feeding operation.

In the several figures some parts have been shown broken away or omitted for clarity.

Referring first to Figs. 31 through 42, all of of which will be more particularly referred to hereinafter, it is thought that a complete understanding of the invention may best be obtained from a brief description of the sequence of operation which occurs during charging and firing of a gun embodying the invention. As shown diagrammatically in Figs. 31 to 42, a plurality of links, seen in end view in the aforesaid figures, are appropriately interconnected to form a flexible belt. Each link includes fingers to grip resiliently a cartridge in its passage from a magazine adjacent the gun to the feeding mechanism thereof. There is provided a fixed stripping cam (Fig. 31) having a nose adapted to pass between a portion of the link and the cartridge casing, the wedge-shaped configuration of the cam, combined with the forward movement of the belt. acting to dislodge the cartridges successively from the resilient grip of the links. The cartridge thus dislodged (Fig. 33) will rest upon a Prior stripped cartridge which has been deposited in the mouth of the receiver awaiting the bolt which is ready to make its forward stroke. Thus the resilient fingers and the two cartridges intermediate those fingers and the mouth of the receiver are in abutting contact, so that the cartridge just stripped, as well as that awaiting chambering by the bolt, is positively but yieldingly held in a predetermined position with respect to the receiver.

Simultaneously the cartridge just stripped will perforce react against the empty link to maintain it and the associated links against forward or backward unintended movement. Further details of the sequence of operation will be clear from a consideration of the explanatory legends appearing on Figs. 31 to 42 of the drawings.

Inasmuch as the entire assembly may be conveniently considered as composed of several cooperative sub-assemblies, the construction of the gun, one exemplification of which is shown and described. will be detailed under appropriate sub-heads.

The gun mount The mounting for the gun as a Whole comprises a cradle l0 (Figs. 1, 2, and 10), preferably made of aluminum or magnesium alloy for lightness, narrower for the major portion of its length and wider toward the front to receive the pair of recoil unit brackets H supported by means of bolts I2 on upturned flanges l3 at either side of the cradle. Flanges [3 also support the pair of slide bearings M (Fig. 3b) attached thereto by means of bolts l5, there being The receiver Forming the principal body portion of the gun, and housing the bolt, the breechblock slides, the breechblock lock, and certain appurtenant parts, is an elongated, generally rectangular hollow receiver 2|, preferably a steel casting having its inner side and upper walls accurately machined for guiding the breechblock slides and bolt. At

its two outer vertical side faces (Fig. 3b), the

receiver 2| is provided with a pair of elongated outstanding ribs 22, each adapted to slide in a slot 23 in the slide bearings M and forming part of the means by which the recoiling portions of the gun are permitted to move with respect to the cradle |0. Receiver 2| is provided in its upper wall with an elongated slot 24 (Fig. surmounted by a T-shaped slot 25 to accommodate the receiver slide 26 to be described.

Juxtaposed to the interior of the two side walls a 21 and 28 of the receiver 2| are the two receiver slides 3| (Figs. 6b and 21) attached to the receiver 2| by means of cap screws 32 and held accurately in predetermined position by means of flanges 33, each engaging a slot 34 in the receiver. Each slide 3| is flanged inwardly as at 35 to support the bolt in its sliding movement, the upper outer edge of each flange 35 being chamfered as at 36 to provide clearance for the rounds during chambering and extraction. The rear end of each receiver slide 3| is provided with a cam formation to be further detailed.

The bolt, breechblock slides, and appurtenant parts Referring to Figs. 9 and 10 particularly, the bolt 4| comprises an elongated one-piece member, as clearly shown, having laterally extending flanges 42 on either side thereof upon which the breechblock slides 43 and 43a are adapted to rest and slide. It will be noted that the thickness of the slides 43 and 43a is equivalent to the lateral width of the flanges 42 and that the over-all width of the bolt 4| measured at the flanges 42 is such as to provide a close sliding fit of the assembled bolt and breechblock slides between the inner surface of the walls 21 and 28 of the receiver 2|.

Bolt 4| is provided on either side thereof with a longitudinal recess 44 for clearing the cartridge ejector to be described, and has a central circular aperture 45 (Fig. 10) to receive the firing pin 46 and driving spring 41 (Fig. 8). The bolt is also provided with a transversely disposed pad 48 to support and guide the rear end of the bolt 4| upon the slides 3| (Fig. 9).

Each breechblock slide 43 and 43a is provided with an elongated aperture 5| therethrough enclosing push rod 52 and compression spring 53 thereabout, the head 59 of the push rod being adapted to lie within a recess 54 (Fig. 6b) of spherical segmental form cut in the forward end of the aperture 5|, the rearward end 55 of each push rod 52 being adapted to pass through an aperture 55 in the lug 51 extending laterally from the bolt 4|. The rearward end of each spring 53 bears against the forward face of the lug 51, and the forward end of the said spring bears against the head 50, whereby the breechblock slides are constantly urged forwardly with respect to the bolt 4|. I

Breechblock slides 43 and 43a are provided with elongated apertures 6|, the aperture associated with the slide 43a being adapted to receive tightly therein one end of the slide key 62, the latter bein secured to the slide 43a by dowel pins 63. The slide key 62 passes freely through the slots 64 in the bolt 4| and BI in the slide 43, it being understood that the clearance between the key 62 and the apertures 6| and 64 is such as to permit the slide 43 and bolt 4| to move freely longitudinally with respect to the key. The right-hand end of the key 62, i. e., the end 65 coextensive in length with the thickness of the breechblock slide 43, is somewhat narrower than the end secured in the breechblock slide 43a.

Passing through elongated apertures (Fig. 3b) one in each side wall of the receiver 2|, is the breechblock locking key 12 having a cross section of flat-sided oval form and locked transversely by means of a plate 13 (Fig. 10) secured at the bottom of the key by means of cap screws T4, the plate 13 being of the same width as the interior of the receiver 2|. Key I2 is provided at its forward end with a recess 15 (Fig. 6b) having a horizontally disposed bottom wall 16 and a rearwardly inclined wall 11 for a purpose to be described.

Pivoted upon a substantially semi-circular recess 8| coextensive widthwise with the flanges 42 of the bolt 4| is the breechblock lock 82 (Fig. 9) havin ga substantially semi-circular forward end 83 to engage the recess 8|. rearward locking surfaces 84 and 85, and carnming surfaces 86 and 81, it being understood from Fig. 9 that the breechblock lock 82 is symmetrical about the vertical axial plane of the gun.

Each of the breechblock slides 43 and 43a is provided with a bottom recess 9| adjacent the.

rear end thereof, and of the contour shown in Fig. 9. there being a forward camming surface 92 and a rearward camrning surface 93.

Adapted to lie within a suitable recess 31 in the bottom face of the bolt 4| is the extractor |0| (Fig. 9) having an aperture I02 transversely thereof whereby the extractor is pivoted on the pin 96 held in apertures H14 in the bolt 4|. The forward end of the extractor |0| is provided with a claw I03 for engagement with the cartridge casing. the claw being transversely arcuate concentrically with the casing. At its rear the extractor is provided with a longitudinal aperture I05 into which is inserted one end of the resilient rod I06 (Fig. 6b) supported at its other end in a suitable aperture l0! in the bottom of the bolt 4|. The firing pin 46 (Fig. 9) is provided with a transverse recess III of slightly greater length (Fig. 7) than the key 62, whereby the pin 46 may slide axially a predetermined short distance with respect to the key. The forward end of the pin 46 is provided with the substantially conical nose ||2 adapted to project through an aperture 3 in the hardened replaceable bushing ||4 pressed into the forward face of the bolt 4| and flush therewith, the aperture I I3 being suitably tapered to correspond to the taper of the nose I I2 (Fig. '7)

The bolt driving spring and bufier assembly For urging the bolt 4| and breechblock slides 43 and 43a forwardly, there is provided the driving spring 41 (Figs. '1 and 8) heretofore noted. the

spring being supported and guided upon the tube II secured at one end in the cap H6 at the rear of the gun. Tube I I5 is supported at its forward end on the rod II1 having an integral head [I8 guided within the aperture 45 in the bolt 4|. Spring 41 may be compressed freely within the aperture 45 and bears at its forward end against the head I I8, the latter in turn abutting the rear face of the firing pin 46. At its rearward end the spring 41 bears against the inner wall II9 of the cap H6.

Adapted to be removably associated with the receiver body 2I is the buffer spring housing I2I engaged with the receiver 2| by means of a vertically separable dovetail joint indicated generally at I22, the buffer housing I2I and its associated parts being locked with respect to the receiver 2| by means of the manually operable pin I20 slidable in the housing I2I and normally urged into engagement with an aperture (not shown) in the receiver by means of a spring (not shown). After the driving spring 41,tube H5, and rod II1 are removed from the receiver by unscrewing the cap II6 from the housing I2I, withdrawal of the pin I26 from its co-operating aperture permits the housing I2I and the parts enclosed thereby to be dissociated from the reeeiver. Reassembly is obviously the reverse of the steps just outlined. There is provided within the housing I2I a buffer spring I23 having a washer I24 abutting the front end thereof, the spring I23 and washer I24 being securely held within the housing by means of the threaded sleeve I25. The rear end of the bolt 4| is provided with an enlarged circular face I26 of sufficient diameter to bear against the washer I24 when the bolt is in its rearinost position.

The ejector assembly Carried within a housing I3I (Fig. 8) attached to the receiver slide 26 is the ejector claw I32, pivoted with respect to the housing upon the pin I33. and bifurcated at its lower end (Fig. to form a pair of forwardly extending claws I34 disposed at each side of the bolt 4| and lying within the recesses 44 of the bolt, there being an aperture MI in the slide to clear the ejector assembly. Housing I3I is provided with a pair of apertures I35 to receive the compression springs I36 adapted to urge the ejector I32 in a clockwise sense and guided therein within apertures I31. Sprin retaining screws I38 are threadedly engaged in the housing I3I, the ejector I32, therefore, being constantly urged about its pivot and limited in such forward movement by abutment against the edge of the aperture I4I of the housing I3I.

The barrel and barrel mounting The forward end of the receiver 2I is provided with a pair of upstanding ears I45, and the adapter I66 (to be hereinafter described) is provided with a pair of laterally extending ears I46 (Figs. 6a and 20), each of said ears I45 and I46 having an aperture I41 therethrough to receive the studs I48. Extending transversely of and bearing against the rearward face of the ears I45 is an upper yoke I52 adapted to receive one end of the studs I48 threaded into apertures I50 in the yoke I52, the studs being pinned by dowels I49. The lower pair of studs I48 is similarly threaded into apertures I5I in either end of a lower yoke I53 extending transversely of the receiver 2|, and abutting the front face I55 of a slot therein.

At their forward extremities the studs I48 are 8 threaded and engaged by the nuts I54, the said nuts being provided with hexagonal depressions. not shown, whereby they may be engaged by a wrench.

Receiver 2I is provided with a cylindrical aperture I6] at its forward end adapted to receive a corresponding cylindrical extension I62 of the barrel I63 and whereby the barrel is accurately positioned axially of the receiver. An annular shim or spacer I64 is positioned intermediate a shoulder I65 of the barrel and the adjacent end of the receiver. In order to support the barrel I63 with respect to the receiver 2 I, there is provided a hollow adapter I56 having a flared portion I61 including apertures (not shown) in alignment with the apertures I41 through which the studs I48 extend, the outer face of the portion I61 being appropriately counterbored to receive the nuts I54. Thus it will be seen that by means of the yokes I52, I53, studs I48, and nuts I54, the adapter I66 may be securely attached to the receiver 2 I.

To permit disassembly of the barrel I63 from the adapter I66, both the adapter and barrel are engaged by means of circumferentially interrupted buttress-thread sections generally indicated at I1 I, and of a common construction sometimes used on breechblocks, whereby upon rotation of the barrel I63 a portion of a turn, the interlocking threads are disengaged and the barrel may be withdrawn. To secure the barrel I63 against rotation, there is provided a dowel I12 adapted to engage a short peripheral slot I13 entering a space between two thread sections "I. thus permitting the barrel to be rotated for un looking but to absorb the reaction due to the spin of the bullet.

To preserve the peripherally locked relationship of the barrel I63 with respect to the adapter I66, the barrel is provided with an axially extending slot I14 with which is adapted to engage the nose I15 of the barrel latch I16 pivoted at I11 with respect to the adapter I66 and guided within a slot I18 therein. A projection I19 limits inward movement of the nose I15 under urging of the compression spring I62 intermediate the front end of the latch I16 and the adapter I66. Accordingly, to unlock the barrel I63 from the adapter I 66, the latch I16 is manually rotated clockwise, as seen in Fig. 6a, to disengage the nose I15 from the slot I14. The barrel is thus free to be rotated and unlocked as aforesaid. To facilitate grasping of the barrel for manual removal thereof from the adapter I66, the same may be peripherally knurled as at I92 (Fig. 2).

Barrel I63 comprises a breech o1 chamber I tapered, as indicated at I83 and I85, to receive the correspondingly tapered portions of the cartridge employed with the gun, the cartridge, when chambered in the breech I86, fitting snugly against the surfaces I83 and I85, and the groove and rim thereof being positioned at the rear end of the breech, the latter being chamfered as indicated at I86 to permit free location of the base of the cartridge, and also being provided with a radially extending recess I81 (Figs. 6a and 20) to receive the claw I63 of the extractor IUI.

The bore I06 of thebarrel continues from the surface I83 to the muzzle (the latter being omitted in all of the figures because of limitations of space). The bore is, as will be understood, of conventional construction, i. e., spirally rifled to yield lands and grooves for imparting to the projectile the appropriate rotary motion for true flight.

For supporting certain components to be herelnafter detailed, the barrel I63 is provided with a bracket 200 (Fig. 15), including a locking device comprising a hook I93 having an arcuate pad I94 adapted to engage the lower portion of the barrel I63, the hook continuing generally upwardly in an extended cylindrical shank I95 guided in an aperture I96 in a laterally extending projection I91 of the bracket 200. Bracket 200 is provided with another projection I98 disposed substantially above the projection I91 and threadedly receiving the adjusting nut I 99 in the central aperture 202 of which the shank I95 is guided at its upper end. Shank I95 is reduced to a flattened portion 203 through which passes the pin 204, and arranged to pivot thereon is the locking lever 205 (Fig. 6a). Lever 205 is provided with a pair of camming surfaces 206 adapted to bear against the upper face of the nut I99, and includes a handle 201 by means of or out of engagement with the nut I99, and the hook I93 accordingly operated upwardly or downwardly to clamp or to release the bracket 200 with respect to the barrel I63.

In order that accurate spacing between the cam surfaces 206 and the pad I94 may be achieved, the nut I99 is, as hereinbefore mentioned, threadedly engaged with the projection I98 so that increase or decrease in said spacing may be effected by rotating the nut I99 with respect to the projection I98. To preserve the desired location of the nut I99, its lower terminus 2 is axially knurled, and adapted to engage with the serrations is the conical tip of the plunger detent 2I2 received in an aperture 2I3 in the bracket 200. The detent is urged outwardly into contact with the terminus 2 by means of a spring 2I4. Thus vibration of the gun is ineffective to disturb the nut I99 and hence the locked position of the hook I93.

The recoil mechanism Referring now to Figs. 1, 2, 5a, 22, and 25, there is provided means for absorbing the recoil of the gun comprising a pair of recoil units 2I8, each including a cylinder 22I extending parallel to the axis of the gun, one disposed on either side thereof and threadedly engaged as at 222 with brackets 223 integral with and protruding laterally from the adapter I66. The brackets 223 are split at 224, the forward portion of the bracket being additionally split as at 225 to permit the same to be drawn together in a clamping action by means of the screws 226, thus to secure the cylinders 22I with respect to the adapter I66 after threaded assembly therewith.

Each cylinder 22I (Fig. 25) is internally threaded at 23I to receive the annular adjusting nut 232 having apertures 233 for engagement by a, suitable wrench. Adapted to bear against the nut 232 is the collar 234 against which the forward end of the resilient structure 235 is adapted to bear, the opposite end of the said structure bearing against a corresponding collar 236 (Fig. 22) abutting a shoulder within the cylinder 22I. A second adjusting nut 238 is rotatable within the nut 232 and also abuts the collar 234, the nut 238 in turn being threadedly engaged upon the recoil unit support 239 comprising a hollow cylinder, as shown, and terminating rearwardly in a bifurcation 240. The bracket I I includes an upwardly disposed ear 221 (Fig. 3a) having a through aperture 228 aligned with apertures 229 in the bifurcation 240 through .20 which the cam surfaces 206 may be brought into which passes the pin 230. Caps 2 I9 threaded upon the nuts 232 serve to close the internal parts of the units ZIS.

The resilient structure 235 is well known in this art and comprises two alternated series of annular members of highly tempered spring steel of shallow V-shaped cross section, as clearly indicated in Fig. 25, alternate members having the apex of the V directed inwardly, and the remaining members having the apex of the V directed outwardly. The structure thus constitutes a resilient assembly adapted to absorb energy with friction and to withstand the heavy recoil to which a gun of the type herein disclosed is subjected. Adjustment in the tension of the structures 235 is effected by means of the nuts 23I and. 238. Inasmuch as the recoil units 2I8 are of a type frequently used in automatic guns, they form no part of the present invention. Sufiice it to state, however, that upon recoil of the gun, cylinders 22I being secured to the adapter I66 will be actuated rearwardly against the force of the structures 235, the shock thereupon being transmitted resiliently to the cradle I0 through the support 239 and brackets I I.

The trigger assembly For initiating and interrupting firing, the gun is electrically controlled through the medium of an electric switch or button actuated by the operator. Accessory controls may be. used, as when firing is to be automatically interrupted as the gun is traversed with its trajectory intersecting some part of an aircraft and to avoid damage thereto. In such cases the firing is initiated by the operator, and control is then transferred to automatic devices designed automatically'to aim one or more guns at the target and to track the same. Cutouts are provided for those guns whose trajectories are likely in some position to intersect a part of the aircraft, and firing is thus automatically interrupted while the trajectory intersects such part.

In any such event, the electrical circuit to the gun includes a switch or switches, a source of current, and the solenoid 24I (Figs. 7 and 21) having an iron yoke 242 carried on the base 243, the electrical conductors being attached by means of a suitable female plug (not shown) engaging a male receptacle 244 attached to theyoke 242. To enable simple detachment and attachment of the solenoid from and to the gun, there is provided a bracket 245 mounted by screws 246 to the receiver 2I. One vertical edge 241 of the bracket 245 is beveled, as shown, to engage a correspondingly beveled rib 248 of the support 243. The latter is provided on its outer face with a pair of adjacent vertically disposed beveled ribs 252 and 253 adapted to mate with a correspondingly chamfered shoe 254. Shoe 254 has a circular aperture 255 loosely fitting a swingable bolt 256 pivoted to the bracket 245 at 251; A flat spring 26I backed by a washer 262 co-acts with a cam lever 263 pivoted at 264 on the bolt 256, the handle 265 being bent at right angles, as shown, for a purpose to appear.

Thus to remove the solenoid, the handle 265 is swung counterclockwise (Fig. 21) to rotate the cam surface thereof away from the washer 262, thereby freeing the shoe 254 which may be disengaged from the ribs 252 and 253. Consequently the bolt 256 and the parts supported thereon may be swung away from the solenoid, the

edge 241 and rib 248 disengaged, whereupon the solenoid is freed for removal. Reassembly is 

